[Population genetic analysis of Drosophila melanogaster longevity: similar effects of endosymbiont Wolbachia and tumor suppressor lgl under conditions of temperature stress].

Before, it has been shown that keeping of Drosophila wild populations under temperature stress leads to prevalence of deletion alleles of tumor suppressor lgl, and higher survival of heterozygous lgl(-)/+ females descendants (haploadaptivity). On the other hand, recent investigations have demonstrated that an additional dose of lgl gene in transgenic males has inadaptive effect--cytoplasmic incompatibility, caused by the gene, is similar to the effect caused by the widespread endosymbiont Wolbachia. Both triple dose of lgl and Wolbachia infection invoke hyperexpression of some cytoskeleton proteins which leads to sperm defects and sterility of hybrid zygotes. Proceeding from this similarity, we studied the Wolbachia effect on Drosophila longevity (LG) depending on the bacteria strain, host genotype and sex, and maintenance temperature. With use of tetracycline, six Wolbachia-free lines were produced, analogical to the infected wild ones. After analyzing LG under optimal temperature conditions (25 degrees C), the lines were subdivided into three genotypic groups, differing by the LG, mortality dynamics, and type of sexual dimorphism. Under conditions of temperature stress (16 degrees C and 29 degrees C) the lines ranks with respect to LG remained as they were, though the distinctions between them were smoothed out. In other words, the effect of the genes regulating LG parameters depends on maintenance conditions. The research also revealed sharp genetic distinctions between LG parameters of two standard laboratory lines Canton and Oregon that were taken as the control. These distinctions do not disappear in crossings. In the infected lines, in seven experiments out of thirty (20% of cases) significant sex-specific influence of Wolbachia on LG was revealed, namely, in two combinations at the optimal temperature 25 degrees C, and in five combinations at stress temperatures. Under the optimal temperature conditions the endosymbiont shortened its host LG in both cases, while at stress temperatures, in four cases out of five, it extended the host LG. Females of the long-living line Bi90 (wMel) from a mountain Kirghiz population appeared to be especially sensitive to the infection carriage--their endosymbiont-caused LG extension was observed both under cold and heat stresses. This result is analogues to the effect of diminishing the oncosupressor lgl dose. In both cases LG extends only under temperature stress, and this positive effect is sex-specific.